Centrifugal pump



March 4, 1924. 1,485,504

A. HOLLANDER CENTRIFUGAL PUMP Fied June 50. 1922 `Platen-ted Mar. 4, -19724.

vented certain new and usefu UNITED s'rA'irEs AiIIiADAIB.iHOIIIIIIANDER,l OF BELLEVILLE, NEW JERSEY.

cENrBIrUGAI. PUMP:

Application led June 30, 1922.v SerialrNb. 571,883.

To all 'whom t may concer/n:

Be it known that I, ALADARHOLLANDER, a citizen of the United States, and resident of the town of Belleville, in the county of Essex and State ofNewv Jerse have in- Improvements in Centrifugal Pumps, of which the following is a specification.

The main object of the invention is to provide a simple and eective hydraulic thrust balancing mechanism adapted for use in centrifugal pumps and for other purposes wherein a packed shaft'is employed.

A further object of the invention is todirectthe fluid which escapes from the thrust balancing mechanism `at the high-pressure side thereof back to said mechanism at the low-pressure side thereof and to utilize this leakage fluid for sealing one or both ends of the mechanism.

The invention as applied to a centrifu al pump, consists inA providing means `where y the thrust on the impellers tending to move the supporting shaft and the impellers toward the intake or suction side of the pump is slightly overbalanced by a thrust inthe opposite direction on a balancing disk carried by the shaft at the discharge end of the pump and subject to the high-pressure Water at that point. The invention further consists in providing means whereby the excess pressure on the balancingv diskin one direction will be balanced by counter-pressure, said counter-pressure being throttled and controlled by the axial movements of the impeller shaft with the result that the impeller shaft will be nicely balanced andl will be held practically in a neutral position be4 tween the counter-balancing thrusts, thereby relieving the shaft and the thrust disk of undue lateral pressure. The invention further consists in utilizing the counter-pressure water for sealing the stalling boxes of the' impeller shaft at both the high-pressure and intake sides of the pump. A great advantage of thisarrangement is that shortlowpressure stufling boxes may. be used, these stuffing boxes being sealed with comparar tively low-pressure water. The waste of 'water' through the stuiling boxes will be comparatively small and of no consequence.

Another important object of the invention is to discharge the excess water from the balancing pressure chamber axially into the suction side or intake ofthe pump so that the energyof the water so discharged will be exerted at the low-pressure side of the pump to assist in directing `the iniowing water through "the low-pressure impeller. In`the drawing Fig. 1 is a longitudinal vertical sectional view of a tandem-balanced multi-stage centrifugal pump embodying the invention;

Fig. 2a detail vertical sectional view of the intake or suction side of the pump; and Fig. 3 is a similar view of the dischar e oroutlet side of the 'pump .showing t e thrust balancing disk and the 'balancing pressure-chamber.

Referring t9 the various parts by numer'als, l designates the lower half of the pump casing and 2 the upper half thereof. The lower half of the 'casing is formed with supporting standards 3; and the upper half is bolted to the lower half by means of bolts 4, the two parts of the casing forming l the several impeller chambers and the intake and discharge chambers which will'lbe more fully' hereinafter described. Extendingthrough the casing and journalled in suitable bearings 5 at each end thereof is the impeller lshaft 6. To one `end of this shaft is rigidly connected a coupling disk 7 by means of which the pump shaft may be connected to any suitable driving motor.

The pump casing is formed with the intake chamber 8 near the left hand end thereof, said chamber being annular and extending around the shaft and in direct open communication with the intake pipe 9 shown in dotted lines in Fig. 1. This intake chamber is connected with an annular pressure chamber 10 and this pressure chamber is connected with an annular intake chamber' 11 of the second stage,'that is to say, of the second impeller. This intake chambe'r 11 is in communication with -a pressure chamber 12 of the second stage, said pressure chamber receiving the water from vthe second impeller. The pressure chamber 12 is connected to an intake chamber 13 of rthe third stage. Thisv intake chamber 13 delivers the water to the third impellerand is f in communication with the high-pressure indicated by dotted lines in. Fi 1.v .p

Rigidly secured to the impel er shaft and arranged to rotate in chambers 10, 12 and '14 are the impellers :16 17 and 18. These impellers l are provided with rigidly araisA (shaft.

ranged discharge nozzles, said nozzles opening at their inner ends on the intake side of the impeiler and receiving water from the intake chambers adjacent thereto. The intake side of the impeller 16 opens directly into the intake or suction chamber 8; the intake sideofY the impeller 17 opens directly irito the intake chamber 11 :and the intake sideof the inipeller 18 opens directly intoY the intake chamber 13. The impellers are spaced' apart and rigidly held in their c spaced relation by sleeves 19 interposed be- Y tween them and mounted on the impeller Each impelleris keyed directly to the shaft, as indicated lin the drawing. -To complete the walls between the chambers 10 and 11 and between the chambers 12 and 13 non-rotating annular partition plates 20 are mounted around the sleeves 19,0said partition plates being formed with annular ribs which fit corresponding grooves in the contacting edges .of the partition walls 21 ofthe casing when the two casing sections are assembled. Communication betweenthe chambers 10 and 1,1 and between 12 and 13 is through the annular peripheral channels indicated by dotted lines in Fig. 1. In the division wall 22, between the intake chamber 8 and the first pressure chamber 10 and extending around the im eller shaft, is a bearing ring 23, said ring Veing formed on its exterior annular surface with a rib which tits a corresponding groove in the contacting surface of the division wall 22. The impeller 16 carries an impeller wearing ring 24, said wearing ring extend-K ing around the eye of the impeller at the left hand edge thereof. This wearing ring fits within an annular fiange 25 formed on the bearing ring 23. and is formed with an annular `flange 26 which fits within a corresponding groove 27 formed in the adjoining face of the bearing ring. The purpose of this ring 24 is to seal the connection' Abetween the intake chamber 8 and the first' pressure chamber 10 so that water from the intake chamber must pass through the impeller nozzles into the pressure chamber and cannot pass around the impeller and back into the intake chamber. The wearing ring has a slightsliding movement in the bearing ring due to the slight axial movement of the impeller shafts, as will be hereinafter described, while at the same time maintaining the seal between the chambers 8 and 10. The impellers 17 and f18each carry a wearing ring 24 which engages a bearing `ring 23 mounted in the partition wall 28' between chambers 11 and 12 and in wall 29 between chambers 13 and 14 so that cpmmunication between these chambers, except through the impeller nozzle, will be sealed at al1 times, notwithstanding the slight axial vmovemen ofthe impeller shaft andthe impellers carried thereby.

iside bf the pump.

In thej operation of pumps of this con- .f

is a larger area exposed to the high-pressure water. This excess pressure results 1n a'. thrust on the impellers and on the limpeller shaft directed toward the suction or intake side of the pump. 1t is desirable to counter-balance or neutralize this thrust,

In the pump casing, at the discharge end thereof, is formed a pressure balancing chamber 30. .This chamber is annular, ex?

Ytending around the impellei shaft, and is.

in open communication withthe high-pressure discharge chamber 14 so'that the highpressure wateriwill freely enter the chamber 30. The annular wall ofthe chamber 30 is formed with an inwardly extending auf L groovedfonits exterior surface to receive Y the rlb onthe wallof the pump casing.

Rigidly securedrto the impelier shaft bv lkeys 33H01* otherwise, is a thrust balanciing disk 33, said* disk forming one wall of the balancing pressure chamber 30 so that the water-'pressure in said chamber 30 Ywill be exerted directiy against said disk and tend to n'iovevthe impelier shaft and the impellers carried thereby" toward the discharge end of ithefpump and in opposition Ito the excess pressure exerted on the highpressure sides of the impellers. `The thrust balancing disk 33 is formed with an annular bea-ring portion 34 which is adapted vto engage the outer 0r right hand side of the thrust ring 32 and thereby close the pressure balancing chamber 30. A counter-balancing pressure chamber 35 is formed between the outer or right hand side of the thrust balancing disk 33 'and the outer wall of' the pump casing. This counter-balancing` pressure chamber is sealed from the chamber 30 when the thrust disk flange 34 is in contact with the thrust ring, and is in communication with said chamber 30 when the thrust/disk is moved to the right away from the thrust ring, tas will be hereinafter described.

A sealing chamber 36 is formed in the pump casing between the intake chamber 8 'and the stuffing box 37- on' the suction This sealing chamber extends around the impeller shaft and is in communication with the intake chamber 8 through an annular throttling means. The sealing chamber isV in openl conimunication with lthe counter-balancing chamber 35 through a pipe 38 so that. water from the counter=balancing chamber will flow directly linto thesealing chamber and from this latter chamber through 1the throttling -device into `the intake chamber and around the impeller shaft. Rigidly sen peller 16 and serves as a spacing meansV cured to the impeller shaft on the suction side of the pump-is a sleeve 39, said sleeve extending through the stuliing box 37 fand through 'the sealing chamber 36. The inner end of this-sleeve is enlarged slightly and is internally threaded to engage threads 40 formed on the adjacent end of the enlarged central portion of the impeller shaft. The inner end of the enlarged portion of the sleeve 39 abuts against the hub of the imtherefor to prevent any axial movement of the impeller on the shaft. The sleeve 39, at a point within the intake or suction chamber 8, is formed with .an annular radial flange or throttling shoulder 41. The .partition wall between the intake or suction chamber 8 and the sealing chamber 36 is formed with an annular, rib 4 which surrounds the impeller shaft. A throttlin sleeve 43 surrounds the im eller shaft an projects into the intake c amberv 8, y said sleeve being formed with an annular exte-4 rior groove which receives the rib 42, said -rib serving as means ltolock the throttle sleeve against axial movement., The interior diameter ofthe throttlingisleeve is'greater than theexterior of the sleeve 39 in order' to provide-an annular water passage of the desired capacity around the shaft and con-` necting the sealing chamber with the intake or suction chamber 8. The inner end of the throttling sleeve extends. intd the intake chamber and -is internally' vthreaded to receive a correspondingly threaded throttle ring or nozzle 43. This throttle ring dr nozzle is adjustable in the throttle sleeve in order to properly position lit with respect to the throttling shoulder on the sleeve 39. As herein-` before pointed out, the im eller shaft and the impellers will have a slig t axial movement dugI tothe water thrusts on the im ellers, and as the throttling shoulder `41l w'` move with the impeller shaft it is manifest that this axial movement will result in variations in the gap or space between .the throttling shoulder-.and the adjacent end of the throttlingA nozzle. v This throttling action will serve to control the discharge of water fromy the sealin'g chamber 36 into. the intake or suction chamber. By properly adjusting the nozzle 43 ththrottlingaction may be `regulated and the desired results' secured. lThe throttling sleeve carries at its outer end an annular abutment or ring 44 which serves as a sto for the packing rings of the stuliing box- 3 on the suction side of the pump. The

inner end of the stuing box 37 is-open to the water of the sealing chamber '36 so that said stulng box -will be sealed by the comparatively low-pressure water inthe sealing chamber. By reason' of this arrangement the stuing box 37 may be made short and need only be kept under ay slight compression, ror low pressure.

Rig-idly`7j secured to the impeller shaft, at f the discharge end of the `purnp,`-is a sleeve 45, the inner Aend of said sleeve beingenlarged and internally threaded to engage the threads 46 on the adjacent' end of the enlarged central portionbf the impeller shaft.

45 extends through the stuffing box 47 on ythe discharge end of the pump, and the inner en d of this stuffingl box i's open to the counter-balancing pressure chamber 35 andy isl sealed by the comparatively low-pressure' water in said'cham er. By reason of this arrangement the stuffing box 45 may be short and may be maintained under a comparatively low pressure or compression.

In the operation of pumps of this type the excess pressure on the high-pressure sides of the impellers will force the impellers and the impeller shaft toward the suction side of the pump. I n the arrangement shown in the drawings, and described herein this'l move-s ment of the impellerlshaft will cause the thrust balancin disk 33 to engage the thrust' ring 32 and c se communication/between the balancing chamber 30 and the counterbalancing chamber 35. This movement ,of l

the im eller shaftwill also open wide the 'throtthng means between the sealing chamber and theintake or suction chamber 8. As

the pressure builds up in the chamber 30 the i force exerted on theethrust balancing disk 33 will tendlto move the impeller shaft and the impellers toward the discharge end of the pump and'in opposition to the excessive pressure on the impellers. Thethrust bal- -ancing disk 'is so proportioned in size and area to the impellers that atany 'speed of the pump,. the force exerted on said thrust balancing disk will be slightly in excess of the contrary excessive thrust on the impel- 1ers so that the thrust diskvwill be' moved 'away from the thrust ring and thereby open communication between the chamber 30 and and, permit high-pressure water to escape vfrom chamber 30 --around the thrust bal-- vthe counter-balancing pressure chamber 35 proach the'nozzle 43ar t ereby throttling or reducing the discharge passage from the sealing chamber into kthe intake chamber.

This will permit pressure to build up in the chamber 35 and 1n the" chamber 36. It is f manifest that when` the balancing pressure in chambery 30 is -suliicient to open up communication between chambers 30 and 35 the throttling means will restrict the discharge from the sealing chamber into the intake chamber. Thispermits the building up of .the necessary pressure in the counter-balancing pressure chamber '35. Itis also clear that when the necessaryl counter-balancing pressure has been built up in chamber the thrttling means will be automatically operated to enlarge the discharge passage from the sealing chamber into the intake chamber thereby automatically preventing building up an excessive pressure inthe counter-balancing chamber 35. In the normal operation of the pump, the impellers and the thrust balancing disk will be maintained, in what might be termed, a neutral position wherein the opposed thrusts will be completely neutralized and the impeller shaft and the impellers will be in, what might be termed, a floating condition, that is to say, the axial thrusts will be completely eliminated.

The counter-balancing water is returned to the intake or suction chamber along the impeller shaft co-axially therewith and in a stream parallel with the main suction kon a ship propeller shaft, or the like.

lVhat I claim is:

1. A centrifugal pump comprising a casing a rotary impeller shaft having a'slight axial movement, an intake chamber at the suction end of the pump, a high-pressure discharge chamber -at the discharge end of the pump, a series of rotary centrifugal impellers mounted on the impeller shaft and directing the Water in successive pressure stages from the intake chamber to the highpressure discharge chamber, a balancing pressure chamber at /the discharge end of the pump and in communication with the high-pressure discharge chamber, a thrust ba ancing disk rigidly mounted on the shaft and subject to pressure in the pressure balancing chamber, a counter-balancing pressureV chamber on the opposite side of said disk from the balancing pressure chamber, the thrust balancingdisk controlling communication between said two chambers, a sealing chamber surrounding the impeller J shaft at the suction side of the pump and in communication with the said intake chamber, means operated by the axial movement pellers mounted on the impeller shaft and directing the waterin successive pressure stages from the intake chamber to the highpressure discharge chamber, a balancing pressure chamber at the discharge end of the pump and in communication with the highpressure discharge chamber, a thrust balancing disk mounted on the shaft for axial movement therewith and subject lto pressure in the pressure balancing chamber, a counter-balancing pressure chamber on the 0pposite side of said disk from the balancing pressure chamber, the' thrust balancing disk controlling communication between said two chambers, a sealing chamber surrounding the impeller shaft at the suction side of the pump and in communication with the said intake chamber, means operated by the axial movement of the impeller shaft to control the flow of water from the sealing chamber into' the intake chamber, and means placing the counter-balancing pressure chamber in communication with the sealing chamber.

3., A centrifugal pump comprising a casing, a rotary impellershaft having a slight axial movement, an intake chamber at lthe suction end of the pump, a high-pressure discharge chamber at the discharge end of the pump, a series of rotary centrifugal impellers mounted on the impeller shaft and directing the water in successive pressure stages from the intake chamber to the highpressure discharge chamber, a balancing pressure chamber at the discharge'end of the pump and in communication with the highpressure discharge chamber, ahthrust balancing disk rigidly mounted on the shaft and subject to pressure in the pressure balancing chamber, a counter-balancing pres- 'su're chamber on the opposite side of said diskfrom'the balancing pressure chamber,-

the thrust balancing disk controlling communication between said two chambers, a sealing chamber surrounding the impeller shaft at the suction side of the pump and in' communication with the said intake chamber,A means operated by the axial movement of` the im eller shaft to control the flow of water rom the sealing chamber into the intake chamber, means placing the counterbalancing pressure chamber 1n communication wlth the sealing chamber, a stuing box for the impeller shaft at the suction end thereof and communicating with the r I n l 1 ing chamber, and a stuing box at the discharge end of the impeller shaft and in communication with the counter-balancing pressure chamber.

4. A 'centrifugal pump comprising a casing, a rotary impeller shaft having a slight axial movement, an intake chamber at the suction end of the pump, a high-pressure discharge chamber at the discharge end' of the pump, rotary centrifugal means mounted on the impeller shaft and directing the water from the intake chamber to the high-pressure discharge chamber, a balancing pressure chamber at the discharge end of the pump and in communication with the highpressure-discharge chamber, a thrust balancing disk rigidly mounted on the shaft and subject to pressure in the pressure balancing chamber, a counter-balancing pressure chamber on the oppositel side of said disk from the balancing pressure chamber, the said disk controlling Acommunication* between said ltwo chambers, a sealing chamber surrounding the impeller shaft at the suction 'side of the pump and in communication with the said intake chamber, a throttling sleeve arranged in said communication, means operated by the axial movement of the impeller shaft to` control the ow of water from the sealing chamber through said throttling sleeve into the intake chamber, and nieans placing the counterbalancing pressure chamber in communication with the sealing chamber.

5. A centrifugal pump comprising a casing, a rotary impeller shaft having 'a slight axial movement, an.intake chamber at the suction end of the pump, a high-pressure discharge chamber at the discharge end of the pump, rotary centrifugal means mounted on the impeller shaft and directing the water from the intake chamber to the high-pressure discharge chamber, a balancing pressure chamber at the discharge end of the pump and in communication with the high-pressure discharge chamber, a thrust balancing disk `rigidly* mounted on the shaft and sub-n ject to pressure in the pressure balancing chamber, a counter-balancing pressure chamber on the opposite side of said disk from the balancing pressure chamber, the said disk controlling communication between said two chambers, a sealing chamber surrounding the impeller shaft at thesuction side of the pump and in communication with the said intake chamber, a throttling sleeve ai*- ranged in said communication, means operated by the axial movement of the impeller shaft to control the flow of water from the sealing chamber through said throttling sleeve into the intake chamber, an adjustable nozzle on the end of the throttling sleeve, and means vplacing the counter-balancing pressure chamber in communication -with the sealing chamber. d

6. A centrifugal pump comprising a casing, a rotary impeller shaft having a slight the impeller shaft and directing the waterv yfrom'the intake chamber to the high-pressure discharge chamber, a balancing pump and in communication with the highres-` sure chamber at the discharge end o the' pressure discharge chamber, a thrust balancing disk rigidly mounted on the shaft and 'subject to pressure in the pressure balancing chamber, a counter-balancing pressure chamber on the opposite side of said disk' from the balancing pressure chamber, the said disk controlling communication between said two chambers, a sealing chamber surroundin the impeller shaft at the suction side o the pump and in communication withthe said intake chamber, a throttling sleeve arranged in said communication, an annularthrottling shoulder carried by the impeller shaft with- 'in the throttling sleeve, an adjustable nozzle at the end of the throttling sleeve, the inner end of said nozzle co-acting with the throttling flange carried by the impeller shaft,

and means placing the counter-balancing' pressure chamber in communication with the sealing chamber.

7. A thrust balancing mechanism comprising a casing, a shaft therein havin a slightaxial movement, an intake' cham r at one end of the lamechanism, a high-pres-l sure discharge chamber. at theother .end of the mechanism, means for forcing iuid from the intake chamber to the high-pressure discharge chamber, a Abalancing pressure chamberat the discharge end of the mechanism and lin communication with the hi h-pressure discharge chamber,.a thrust ba ancing disk rigidly mounted on the shafty and subject. to the pressurein the pressure balancing chamber, a counter-balancing pressure chamber on .the opposite side `of said disk from the balancing pressure chamber, the thrust balancing disk controlling communication betweensaid two chambers, a sealing chamber surrounding the shaft at the intake side of the mechanism and in communication with the intake chamber,

means operated by the axial movement of the shaft to control theV iow of water from the sealing chamber into the intake chamber, and means placing the counter-balancing pressure chamber in communication with the sealing chamber.'

8. A thrust balancing mechanism comprising a. casing, a shaft therein havin a slight axial movement, an intake cham erat one end of the mechanism, a high-pressure chamber at the yother end of the mechanism, means for forcing Huid from the intake lchamber to the high-pressure discharge chamber, a balancing .pressure chamber 'at iso the dischargeend of the mechanismv and in communication with the YVhigh-pressure chamber,l a thrust balancing disk rigidly*V mounted on the shaft and subject to theY pressure in the pressure balancing chamber',

y the sealing chamber, a stuiing box surrounding Ythe shaft at the high-pressure end of the mechanism andY in communication with the counter-balancing pressure chamber, and a stuffing box surrounding the shaft at Vthe intake end of the, mechanism and in communication with theV sealing chamber.

9. A thrust balancing mechanism comprising a casing, a shaft extending through said casing, an intake chamber at one end of said mechanism, a pressure discharge chamber at the other end of said mechanism, means to forcer-fluid from the intake chamber to the discharge chamber, abalancing-pressure chamber at Ythe discharge end of said mechanism and in communication with the pressure discharge chamber, a thrust balancing means connected to and .movable axially with said shaft and subject to pressure in the balancing'` pressure chamber,- a counter-balancing pressure chamber on thefopposite side of the /thrust balancing means, thel said thrust balancing means controlling communication between said two chambers, a sealing chamber at the intake end of the mechanism and surrounding the shaft, and4 means for maintaining a substantial equality of pressures in the counter-balancing pressure chamber andthe sealing chamber.

10. A thrust balancing mechanism comprising a casing, a shaft thereinhavin a slight axial movement, an intake cham Yer at one end of saidV mechanism, a pressure dischar e chamber at the other end of said mechanism, means to force iluid from the intakechamber to the discharge chamber, a balancing ressu're chamber at the discharge end of saig mechanism and in communicaltion with the pressure discharge chamber, a Ythrust balancing means connected to and movable axially with said shaft and'subject to pressure in the balancing pressure chamber, a'counter-balance pressure chamber on the opposite side of YVthe 'thrust-balancing means, the saidthrust balancing means con- -trolling communication between said two chambers, a sealing chamber at the intake end of the mechanism and in' communication with the intake chamber, means placing the counter-balancing pressure chamber in constant communication with the sealing chamber, and means for controlling the communication between the sea-ling chamber and the intake chamber the said means being operated by thc thrust-balancing means and in YYunison therewith to throttle the communimeans to force fluid from the intake cham-v ber to the Ydischarge chamber, a balancing pressure ,chamber at thedischarge end of said mechanism and in communication with the pressure discharge chamber, a thrust balancing means connectedto and movable axially with said shaft and subject to pressure in the balancing pressure chamber, a counter-balancing pressure chamber on the opposite side of the thrust-balancing means, the said thrust balancing means controlling communication between saidY two chambers, a sealing chamber at the intake end of the mechanism and surrounding the shaft, means placing the counter-balancing pressure chamber in communication with the sealing chamber, and means operated'by the axial movement of theV shaft to control the dow oiluid frcm the sealing chamber into the inta-ke chamber. i

12. A thrust balancing mechanism-comprising a casing, a shaft extending through said casing, an intake chamber at one end ofn said mechanism, a pressure discharge chamber at the other end of said mechanism, means to force fluid from the intake chamber to the discharge chamber,- a balancing pressurechamber at the discharge end o said mechanism and in communication with the pressure discharge chamber, a thrust balancing means connected to and movable axially with said shaft and subject to pressure in the balancing pressure chamber, a counter-balancing pressure chamber on the o posite side of the thrust balancing means, t e said thrust balancing means controlling communication between said two chambers, a sealing chamber at the intake end of the xmechamsm and surrounding the shaft and in communication with theintake chamber through a central annular passage iextending around the shaft, and means placing theYcounter-balancing pressure chamber i in communication with the sealing chamber.,

' 13.' A thrust balancing mechanism comprising a casing, a shaft extending through said casing, an intake chamber atL vone end of said mechanism, a pressure discharge chamber at the other end of said mechanism, means' to force fluid from the intake chamber to the discharge chamber, -a balancing pressure chamber at the discharge end of said mechanism and in communica-A tion with the a thrust balanclng means connected to and movable axially with said shaft and subject. to pressure in the balancing pressure chamber, a counter-balancin pressure chamber on the opposite side of t e thrust balancing pressure discharge chamber,

means, the said thrust balancing means controlling communication between said two chambers, a sealin chamber at the intake en'd of the mechanism and surrounding the shaft and in communication with the vintake chamber through a central annular assa e extending around the shaft, an annu ar a justable means for r`Varying the flow from the sealing chamber into the intake chamber, and means placing the counter-balanc' pressure chamber .1n communication wit the sealing chamber.

A In testimony whereoI hereuntoiailizi my A v'signaturer ALADAR HoLANDEli. 

